In recent years, liquid crystal display devices, for example, which are thinner and lighter than conventional cathode-ray tubes, are in wide use as flat panel displays for liquid crystal television monitors, portable phones, and the like. These liquid crystal display devices include a lighting device that emits light (backlight device), and a liquid crystal panel that functions as a camera shutter against the light originated from the light source in the lighting device to display desired images.
The lighting devices are broadly classified into a direct type and an edge light type, depending on the arrangement of the light source relative to the liquid crystal panel. For example, in the liquid crystal display device for use in portable phones, notebook PCs, or PDAs, the edge light type lighting device, which can be made thinner more easily than the direct type lighting device, are generally used. That is, in the edge light-type lighting device, the light sources are disposed along the sides of the liquid crystal panel, and therefore, the lighting device can have a thin structure. Also, the light originated from the light source is guided towards the liquid crystal panel though a light guide plate having a light-emitting surface facing the liquid crystal panel.
One of the conventional lighting devices disclosed, the one described in Patent Document 1 below, for example, uses light-emitting diodes (LED) as the light source. In this conventional lighting device, a plurality of light-emitting elements (LED chips) of light-emitting diodes are disposed along the longitudinal direction of a long and thin square bar-shaped printed substrate. Further, in this conventional lighting device, reflecting plates are disposed on both sides of each of the light-emitting elements such that the reflecting plate and the light-emitting element are arranged alternately. This way, a high-luminance linear light beam with little luminance variation can enter the light guide plate.